You may have heard that sitting for long periods makes you more likely to develop a blood clot deep in the veins of your body. This is known as deep vein thrombosis (DVT). Surgery is a recognized risk factor for this condition, which usually affects the lower leg or thigh. But many other DVT risks are not as well known.

“I do believe there is less awareness of deep vein thrombosis and its potentially fatal consequences than there should be,” says Susan Kahn, MD, a professor of medicine at McGill University and a senior investigator in the Centre for Clinical Epidemiology at the Lady Davis Institute for Medical Research in Montreal.

The results of blood clots, also called venous thromboembolism, can include fatal blockages of blood flow in the lungs.

Being able to identify the risk factors can help you make healthy choices and cut your chances of developing a dangerous clot. Check out this list of DVT risk factors.

1. A Hospital Stay, With or Without Surgery

A hospital stay is a DVT risk factor because you often lie in bed for long periods of time. The National Blood Clot Alliance reports that being confined to a bed or wheelchair for long periods of time during a hospital stay is a leading risk factor for deadly blood clots. In fact, an estimated 1 in 10 hospital deaths are related to blood clots in the lungs, according to the Centers for Disease Control and Prevention. Additionally, nearly half of all blood clots are estimated to occur during a hospital stay or within three months of a hospital stay or surgery.

If you’re ever hospitalized, ask your healthcare provider about strategies to reduce the risk of DVT. This may include wearing elastic compression stockings or using sequential compression devices. These devices work by squeezing your muscles as a way to keep blood circulating in your legs. If you’re ever in the hospital, the medical staff will encourage you to get out of bed and walk as soon as you’re able. That’s because moving increases blood flow and, in turn, reduces your chances of developing a blood clot.

2. Being Overweight and Not Physically Active

“If there was no obesity in the world, venous thromboembolism rates would plummet,” says Mary Cushman, MD, a hematologist at the University of Vermont Medical Center in Burlington and the medical director of its thrombosis and hemostasis program. According to a study published in May 2015 in the Journal of Internal Medicine, there is a relationship between obesity and the risk of DVT. Although the reasons why being overweight increases DVT are not totally clear, there is strong evidence showing that the risk of DVT increases as a person’s weight increases.

3. Traveling by Train, Plane, or Car

Traveling can be fun. But all that travel can have a downside if you don’t move enough. The good news is that there are simple things you can do to stay healthy on your trips. When asked what precautions people who travel a lot should take to reduce their risk of DVT, Dr. Cushman gave a few tips for everyone to keep in mind.

“On average, the best remedy is to keep moving,” she says, suggesting that travelers get up and walk around every one to two hours while on a plane for a long journey, or pull over and walk or stretch every two hours while driving.

The National Blood Clot Alliance provides similar tips in its Stop the Clot campaign. The group recommends that people get up and move around at least every hour when traveling on a plane, train, or bus. If you can’t get up for some reason, try pointing and flexing your toes or making circles with your feet. This will help keep the blood circulating in your legs. A study published in September 2016 in the Cochrane Database of Systematic Reviews found high-quality evidence that compression stockings help reduce DVT among airline passengers on flights lasting more than four hours.

Cushman also noted that if you’ve had a prior venous thromboembolism, have other risk factors, or are planning to go on a long trip, you should talk with your healthcare provider to see if anything special is needed. For example, depending on your situation, your healthcare provider may recommend aspirin, compression socks, or a low dose blood thinner.

4. Excessive Television Watching

A study published in April 2018 in the Journal of Thrombosis and Thrombolysis showed that watching too much TV is associated with blood clots. This increased risk is partly due to the fact that long periods of sitting can decrease blood flow to the legs and feet. In the study, people at the greatest risk for developing blood clots were those who watched TV very often compared with those who never or seldom watched TV. This relationship remained true for people who met the recommended level of physical activity. This means that watching too much TV is still a risk factor for blood clots even if you’re physically active and attempt to move while watching your favorite shows. The researchers concluded that everyone should reduce the amount of TV they watch, increase their physical activity, and maintain a healthy weight.

5. Height

Findings from a study published in July 2017 in the Journal of Thrombosis and Haemostasisshowed that a person’s risk of blood clots increased by 30 to 40 percent for each 10 centimeter increment in height. This study was done with adults of European ancestry. In the study, height was more strongly associated with DVT than with pulmonary embolism. Although the link between blood clots and taller height is relatively new, there are a few possible explanations. For example, it is possible that taller people have a greater venous surface area and a higher number of venous valves overall.

New Ways to Treat Blood Clots

“We've had a revolution of new drugs in the last 5 to 10 years, which has simplified the treatment of blood clots,” says Cushman. “These medications, called direct oral anticoagulants, are less cumbersome to use compared to the old standard warfarin (Coumadin, Jantoven) treatment, which requires regular blood work for monitoring.”

Talk to your healthcare provider about what you can do to reduce your risk of developing a DVT.